The concept of linear load refers to the force required in the reeling, which loads the paper reel formed on the reeling shaft. Said force required in the reeling is applied to the reel formed on the reeling shaft primarily via the reeling cylinder in such a way that the necessary force, linear load, is generated via the nip between the outer perimeter of said reeling cylinder and the outer perimeter of the reel that is being formed, when the loading of said nip is at least primarily generated by means of force devices acting on the ends of the reeling shaft. In the initial reeling device the formation of the bottom portion of the reel on the reeling shaft takes place, whereafter the reeling shaft is transferred to the loading device to be reeled to form a full paper reel.
The force loading the nip can be adjusted by means of control signals derived on the basis of the position of the initial reeling device and the loading device in such a way that the loading of the nip is dependent in a predetermined manner on a possible initial reeling angle, the diameter of the growing reel, or time, i.e. the linear load changes as a function of a measurable factor. At the transfer stage, in which the reeling shaft and the reel to be formed thereon are transferred from the support and loading applied by said initial reeling device or the like to the loading effected by the loading device, a force peak which disturbs the reeling process is often generated in the linear load.
Said reel-up is generally used for example for reeling up of a paper web passed for example from a paper machine or a finishing device for paper. The reel-up in question is a continuous reel-up in which machine reels are reeled successively. When the reel has become full, the web is changed to travel to a new reeling shaft. The web is reeled around the reeling shaft and in the reel-up the reel which is gradually growing into its full size, is pressed against the reeling cylinder by means of a loading device, the web travelling over the reeling cylinder in a particular sector and the reeling cylinder being rotated at a  peripheral speed corresponding to the desired speed of the web. Before the reel is completed, a new reeling shaft can, when accelerated to the running speed, be brought in nip contact with the reeling cylinder by means of the initial reeling device in such a way that it also attains the corresponding peripheral speed. As soon as the paper reel has attained the desired diameter, it is transferred away from the reeling cylinder. Thus, its peripheral speed starts to become lower, which results in that a web loop is formed between the new reel shaft and the complete reel. This loop is guided e.g. by means of a pressurized air jet to wind around a new reel shaft, and it is torn off from the finished reel as a result. There are also other known ways of change.
Because of the variations in the loading, it is a problem in the aforementioned transfer stage especially when reeling takes place at high speeds, that wrinkles are produced in the inner layers of the reels in such a manner that the bottom portion of the reels is rejected as a broke. The amount of paper discharged as broke may be as high as 2 to 3%, which causes considerable financial losses for the paper mill.
A known method for changing the linear load on the reel-up is disclosed for example in the patent FI-71107, and in the corresponding U.S. Pat. No. 4,634,068. Here, secondary forks are driven against the reeling shaft which is initially reeled in primary forks, in such a manner that the forks hit the reeling shaft. The linear load is controlled in this transfer stage by evenly reducing the loading produced by the primary forks, and by evenly increasing the loading of the secondary forks at the same time, wherein the sum linear load remains substantially equal. The impact on the reeling shaft, however, always results in a clear linear load peak. Thus, in addition to the change of the loading, the disturbance is also caused by the transfer of the loading device to a position where it can receive the reel from the initial reeling device, and the latter factor can act in the transfer of the loading, even though the linear load could be controlled well by controlling the actuators affecting the loading at the transfer stage. 
For example in the generally used reel-up type, there are reeling carriages which can be moved in the longitudinal direction of the machine (machine direction), which reeling carriages function as a loading device when the reel is completed after the initial reeling. The carriages are provided with guide jaws, which press the ends of the reeling shaft towards the reeling cylinder. The guide jaws press the reeling shaft with a force, which is determined according to the force of the actuators used for moving the reeling carriages. When the actuators are used to drive the carriage against the reeling shaft, a certain pressure always prevails therein to ensure the movement, the pressure causing a “load stroke” when the guide jaws touch the reeling shaft.